Photoelectric controlled device for knitting machines



p 16, 1952 w. E. STANLEY ET AL 2,611,097

PHOTOELECTRIC CONTROLLED DEVICE FOR KNITTING MACHINES Filed Nov. 26, 1946 Inventors -$TANLEY EDWARDS W E C. H Mil/11 Attorneys Patented Sept. 16, 1952 rnorosnsc'rmo CONTROLLED DEVICE FORKNITTING MACHINES William Ewart Stanley and Cyril Houghton Edwards, Spondon, near Derby, England, assignors to Celanese Corporation of America, a corporation of Delaware I Application fiovember 26, 1946, Serial No. 712,432

' In Great Britain May 23, 1946 3 Claims.

This invention relates to stop machinesor signalling devices-for knitting machines and the like and is particularly concernedwithstop motions or signalling devices for warp knitting machines.

In our prior U. S. Patent No. 2,290,257 there is described astop motion or signalling device for a knitting machine or the like which comprises a photo-electric cell, means for traversing said cell repeatedly across a fabric being made on the machine and close to the line at which said fabric is being formed, means for directing light coming from said fabric into said cell and operative means controlled by said cell and adapted to act on undue variation of the amount of light entering saidcell' by reason of faulty fabric. By this means the whole .of V the fabric may be traversed by the cell, and, if a thin or thick place should be encountered at any point in the fabric dueto a. missing thread or an extra thread or any otherfault, the lighttransmitted through or reflected from the fabric, and consequently the light entering; the cell, will alter in intensity and the operative means will act either to stop the machine or to give a warning signal.

The present invention relates to an improved stop motion or signalling device of the above type and comprises, in combination witha suitable light source, an optical system arranged to form an image of said light source in the vicinity.

of the fabric being examined, the photo-electric cell being arranged to receive light after it has passed through the fabric. Such an arrangement has a number of advantages; thus, by using a small, well-defined light sourcathe area of the fabric being examined at any-instant may bemade very small, so that high selectivity can be obtained without the loss of sensitiyity which would be occasioned by using a photo-electric cell enclosed in a casing having a light-receiving slit only large enough to permit the same area to be scanned. An electric lamp with asmall,

. v 2 I this meansthe-photo-electric cellmay be placed in any convenient position along the path of the light beam, while at'the same time the light can be spread over'the entire cathode. V I

The apparatus described can be employed where the light source and photo-electric cell are on the'same side of the fabric and amirror is placed on the other side of and'in contact with the fabric, so that light from the source which is reflected into the photo-electric cell passes through the fabric twice-the optical system as sociated with the light source being arranged to forman image on the mirror face. In this case the projectoni. e. the light source and its optical system, and the receiver, i .'-e.', the photo-electric cell and its optical system, are mounted for traversing across the fabric so that the optical axesof the projector'and receiver always are in a common plane and meet onthe mirror face at equal angles to its normal. To achieve this object it is convenient to mount the'projector and receiver as a-single unit.- However, even with optical systems of shortfocal length andwith the apparatus asnear the mirror as the physical dimensions of 1 the' projector and re-' ceiver will permit, the bulk and weight of the apparatus makes difficult its mounting so that it can be traversed whilst maintaining-there'- quired accuracy of position.

An important modification of the-invention,

therefore, comprises an assembly inwhich the projector and receiver are combined into a single unitwith a single optical system, half of which .is used for projectionand the other half for receiving. .A light source is placed on the axis of a convergent optical system at a distance greater than its focus, and the mirror over which the fabric is to pass is'arranged on the opposite side of the optical system with its surface perstraight filament is very satisfactory as light source. v

It is unnecessary to place the photo-electric cell very close to the fabric and it is preferred to provide an optical system adapted to direct light onto the photo-electric cell. The light passing through the fabric and travelling toward the a parallelbeam to fall on the cathode, as by pendicular to the axis andso distant that an.

imageof the light source is formed on its surface; With such an arrangement, light falling on the mirror is reflected back along a path symmetrical with that along which it arrived and so would be brought back to focusexactly at the source. By screeningv part, e. g. half, of the lens from the light source this part of the lens may be used to receivelight reflected from the .mir-.. ror and focus it into a photo-electric cell.

Where the cell;and lens are of suitable dimensions the; cell can'be placed directly in the path ofTthe light travelling from the source to the lens and may itself act as screen; Generally,

however, a separate screen, arranged across a diameter of the lens, is preferred.

A preferred form of this arrangement is one in which a. second mirror is employed for the purpose of screening half the lens. This mirror is placed close to the lens and inclined at asuitable angle to the optical axis, thelight source being placed to one side so that the light travels from the source to the mirror and thence through the lens by which it isfocused to produce animage of the light source on the mirror over which the fabric is to pass, With this arrangement, light reflected from the screening mirror'appears to have emanated from a point on the slide so arranged that the mirror image of the source can be made to travel along theoptical axis of the lens system, either the image can be formed on the cathode of the photo-electric cell, or any desired area of the cathode may be illuminated. Again the arrangement may be modified so that the photo-electric cell is illuminated by a parallel beam of light, object canbe achieved by using a bi-focal-lens, the focal length of the receiving half being twice that of the transmittinghalf. referably the opti al system used is composed of equal convergent lenses, one half of one lens on the receiving side of the assembly, being omitted. H

Apart from the arrangement of the projector and receiver in the manner described, the apparatusgused for the purposes of the present invention may be substantially as described in our prior U. 3. Patent No. 2,290,257. Thus, in conjunction with the photo-electric cell, there may be used a valve amplifierfor amplifying the effect produced by change in intensity of the light falling on the cell, and the output from the amplifier may be used to operate a relay of any desired type, which in turn may be used for stopping the machine on which the fabric is being formed or for giving a required signal.

The accompanying drawing illustrates diagrammatically one form of stop motion in accordance with the invention,

' Referring to the drawing, the apparatus shown comprises av casing l having mounted therein a lamp 2 diustably carried in slide 3 and a photoelectric cell 4 shielded-131cm lamp 2 by a mirror 5-, the reflecting side of which faces toward the m-P 2- ror '5 extends across the diameter of-a semi-circular convex lens 6, the plane face of which is contiguous with the plane face of a circular convex lens 1 of identical focal length; the lens 7 closing an a erture in the. casing I provided therefor. The lamp 2v has a short straight filament B'WljllChyiS. shown in the drawing in end view, the lamp beingso arranged that an image of th filament-Bis formed on a mirror 9 arranged to co op rate with the componentscontained in the casing.- lso as to reflect the image back through lens T- to the'cathode [0 of i the photorele'ctric cell 4'.

The casing l is arranged to be traversed repeatedly in the-manner'described inprior U. S. Eat-lent No. 2,290,257 across the face of a fabric H. being producedon a warp-knitting machine, thecasing travelling alonga path parallel to the mirror 9 arranged just below and in contact with the. fabric andextending across the whole width thereof. The photo-electric cell isconnected via a. valve. amplifier with a relay which may be adapted to stop the warp-knitting; machine or to give a required signal.

In operation-the lamp 2 is adjusted along the slide 3 until the device is focused so that an,

image of the filament appears on, themirror 9. Byreason of the fact that the light returning from the mirror 9 andfalling on the cathode H) of the photo-electric cellA passes through a lens system having twice the focal length of that through which it passed on its way to the mirror, it emerges from this lens system in the form of a. parallel beam of light which illuminates the cathode l0- evenly, this object being achieved even though only a very small area of fabric is being examined, the area in fact being that occupied by the image of the filament. If, during the course of the knitting operation, an unduly thick or thin place in the fabric is scanned by the device, the light falling on the photo-electric cell is accordingly diminished or increased, thus causing a change in the output of the amplifier connected to the photo-electric cell, and this change may be causedto operate a relay for the purpose of stopping the knitting machine or giving a suitable signal.

Having described our invention, what we desire to secure by Letters Patent is:

1. In astopor detector motion for a knitting machine comprising a photo-electric cell arranged to be traversed repeatedly across the fabric being formed on the machine-and close to the line at which said fabric is being knitted, a first mirror on the opposite side of said fabric to said cell, means for directing light through said fabric to said first mirror and thence back through said fabric to said cell, and operative means controlled by said cell and adapted to give a warning indication of undue variation of the amount of light entering said cell by. reason of faulty fabric, the'improved construction which comprises a casing mounted for traversing repeatedly across the fabric, said cell being mounted within said casing together with a small, well defined light source, a second mirror situated between said cell and said light source and a. lens mounted on said casing and partly shielded from direct light from 'said light source, said'first and secondm'irrors' and said lens together forming an optical path between said light source and said cell whereby light from said light source forms an image in the vicinity of said fabric and is reflected by said first mirror back through said fabricto illuminate a substantial area of the cathode of said cell.

2. Apparatus according to claim 1, wherein the reflecting surface of said second mirror is inclined towards the light source and the shieldedportio'n-of the lens is of twice the focal length of theunshielded portion so that the light travel,- ling towardsthe cell is in the form of a beam of parallel rays.

3; Apparatus according to claim 2, wherein the light source comprises a: short, straight filament of an; electric light bulb.

WILLIAM EWART STANLEY. CYRIL HOUGHTON EDWARDS.

REFERENCES CITED Thev following references are of record in the file of. this patent:

UNITED STATES PATENTS 

